Method of manufacturing a CVD torch

ABSTRACT

An improved torch for the mixing of oxidant and fuel gases external to the torch, for exampled for use in chemical vapor deposition processes, and its method of manufacture are disclosed. A first torch body portion is formed having a manifold cavity with one side open. A number of tubes extend from passages formed in a torch face plate through the first manifold cavity. A first liquid material (such as wax) is poured into the cavity, such that its upper surface defines the desired inside wall surface of the first manifold corresponding to the open side. This material is allowed to harden. A second liquid material (such as epoxy) is then poured over the first material, and hardens to form the remaining wall of the first manifold cavity and to seal the tubes to the torch body portion. The first material is then removed, providing a torch body portion having a manifold with tubes extending through it. A second manifold may then be assembled to the first torch body portion to provide connection to the tubes. 
     In a particularly preferred embodiment, the first tip body portion may contain a further passageway for receiving a fluted tube to define additional passageways for the supply of additional unmixed materials to the vicinity of the flame.

FIELD OF THE INVENTION

This invention relates to a torch for mixing and burning oxidant andfuel gases. More particularly, this invention relates to a method ofmanufacture of a torch for burning a fuel gas in an oxidant gas, inwhich the mixing of the oxidant and fuel gases takes place external tothe torch and to the torch so manufactured. Such a torch is particularlyuseful in connection with chemical vapor deposition (CVD) techniques.

BACKGROUND OF THE INVENTION

It is known that in some cases it is desirable to mix a fuel gas to beburned with an oxidant external to the torch. For example, in U.S. Pat.No. 3,204,682 to Teleshefsky et al, a torch is shown which is suitablefor this purpose. The Teleshefsky et al torch comprises a body portion 4having a torch face plate portion 5. A number of gas tubes 17 are weldedor soldered into a plate 9 separating first and second manifolds 10 and13. The tips of the gas tubes 17 extend through holes 18 in the torchface plate 5. The holes 18 are broached to provide spaced annularpassages 20 around the tubes 17, such that the annular passages extendfrom the manifold 13 to the exterior surface of the torch face plate 5,and the tubes 17 extend from the first manifold 10 through the secondmanifold 13 and to the exterior surface of the torch face plate 5.

As described in the Teleshefsky et al patent, the torch assembly is madeentirely of metal, and the tubes 17 are preferably silver-soldered tothe plate 9 separating the first and second manifolds. This assembly isthen assembled to the torch body portion 4. In order that this assemblycan be made, the alignment of the ends of the tubes 17 to be received inthe holes 18 drilled in the face plate 5 is critical. Such a torch mightbe difficult to manufacture. Moreover, the Teleshefsky et al torchrequires that the oxidant and fuel gases be supplied in concentricpassages; this is not always desirable, and places a significantconstraint on the flame pattern.

It is sometimes additionally desirable to supply materials other thanthe oxidant and fuel gases to the vicinity of the flame. The Teleshefskyet al patent teaches no method of supplying such additional materials tothe flame for deposition or any other purpose.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide an improvedtorch for mixing of oxidant and fuel gases external to the torch whichis more readily and economically manufacturable than that shown in theTeleshefsky et al patent, and which does not restrict the designer'schoice of the pattern of delivery of the fuel and oxidant gases.

It is a further object of the invention to provide a method ofmanufacture of a torch as above, and which additionally allows supply ofone or more additional chemicals to the vicinity of the flame withoutrequiring mixture of the chemicals with one another or with either theoxidant gas or the fuel gas prior to their supply to the flame.

The above objects of the invention and others which will become apparentfrom the following description thereof are achieved by the method ofmanufacture of a torch according to the invention, in which a firsttorch body member is formed defining a first manifold cavity having oneopen side. A face plate of the body member opposite the open side of themanifold has a number of passageways formed therein. Gas tubes areinserted into some of the passageways, and extend through the firstmanifold cavity. A first material, for example, a liquid is then pouredinto the cavity to a degree that its upper surface corresponds to thedesired inner surface of a membrane to be formed closing off the openwall of the manifold cavity. The first liquid is then allowed to harden.A second liquid is then poured over the hardened first liquid, andextends around the tubes. The second liquid is allowed to harden,forming a membrane sealing the tubes to the wall of the manifold cavityin the first torch body portion, and closing off the first manifold. Thefirst liquid is then reliquefied and removed, leaving behind a firstmanifold through which the tubes extend. A second manifold is thenassembled around the ends of the tubes extending through the hardenedmembrane.

The torch may include a central cylindrical passageway for receiving afluted tube. The fluted tube has a central passageway for the supply ofa first material to the vicinity of the flame, while passageways formedbetween the flutes and the cylindrical passageway form additionalpassageways through which one or more additional materials may besupplied to the vicinity of the flame without mixing with the firstmaterial prior to their supply to the vicinity of the flame.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood if reference is made to theaccompanying drawings, in which:

FIG. 1 shows a cross-sectional view of the overall torch assemblyaccording to the invention;

FIG. 2 is a partial cross-sectional view taken along the line 2--2 ofFIG. 1;

FIG. 3 shows a cross-sectional view of a first torch body member in afirst stage of manufacture, having had the gas tubes inserted in holesextending through the face plate thereof;

FIG. 4 shows a subsequent stage in manufacture of the first torch bodymember according to the invention, after casting of the first and secondliquids; and

FIG. 5 shows the first torch body member when complete, after the firstliquid has been removed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a cross-sectional view of the overall torch assembly, whileFIG. 2 is a cross-sectional view taken along the line 2--2 of FIG. 1.

As can be seen in FIG. 1, the torch assembly comprises a first torchbody portion 10, which comprises a torch face plate indicated generallyat 12. A number of passageways 14 extend from the outer surface of theface plate 12 through it and into a first manifold 16. A number of tubes18 extend from some of the passageways 14 in the face plate 12 through amembrane 20 and into a second manifold 22. The second manifold 22 isdefined by a cavity in a second torch body portion 24 and by membrane20. Second body portion 24 is sealed to the first body portion 10 bymeans of O-rings or equivalent seal devices 21, 23 and 25. A fuel gas Asuch as hydrogen may be supplied through openings 10c extending into thefirst manifold 16, and an oxidant B such as air or oxygen may besupplied through second openings 24a extending into the second manifold22. The fuel gas A then flows out by way of holes 14 in the face plate12 into the vicinity of the torch face plate 12, and is mixed andcombusted with the oxidant B, flowing from manifold 22 via tubes 18 tothe vicinity of the torch face plate 12. Accordingly, the fuel gas A andoxidant B mix only externally to the torch, that is, outside the faceplate 12. Cooling water may be supplied to a cooling water passage 27 inthe first body portion 10 via an inlet port 29 in the second bodyportion 24, and removed therefrom via an outlet port 31. A temperaturesensor may be disposed in a recess 33 in the first body portion 10.

According to a further aspect of the invention, the first and secondtorch tip body members 10 and 24 may be generally circular, as shown inFIG. 2. A cylindrical passageway 26 can be formed extending through bodymembers 10 and 24 for receiving a fluted tube 28. Flutes 30 formed onthe exterior surface of the tube 28 cooperate with the cylindricalpassageway 26 formed in the first and second torch tip body 10 and 24 todefine a number of additional passageways 26a for the supply of achemical D to the vicinity of the flame formed external to the torch tipface plate 12. A second chemical C may be supplied to the flame via thecentral passageway 32 formed in the tube 28.

The passageways 26a formed between the cooperating flutes 30 of the tube28 and the central passageway 26 in the torch body portions 10 and 24may communicate with a third manifold 34 formed by a recess in a thirdbody portion 36 (as shown) or in the second body portion 24, such that agas or other chemical D supplied to a passageway 38 in the third bodyportion 36 may be supplied to all the passageways 26a.

As shown in FIG. 1, the flutes 30 may be terminated at or after themanifold 34, such that the tube 28 can be sealed to the third bodyportion 36 by means of a compressible resilient seal member 40, which iscompressed into the third body portion by a cap member 42. The thirdbody portion 36 can be sealed to second body portion 24 by a furtherO-ring 46 as indicated. Screws or the like (not shown) extending fromthe first body portion 10 through the second body portion 24 and intothe third body portion 36 may be employed to hold this assembly togetherpermanently.

FIGS. 3-5 show stages in the manufacture of the first tip body portion10. FIG. 3 shows the basic tip body portion. As can be observed, the tipbody portion has formed in it a central passageway 26 for receiving thefluted tube 28, and also has an annular first manifold cavity 10a formedtherein. A number of passageways 14 extend from the first manifoldcavity 10a to the face plate portion 12 of the tip body member 10. Anumber of tubes 18 are inserted into a like number of the passageways 14in the face plate portion 12 of the first tip body portion 10. One ormore gas passageways 10c extend into the manifold cavity 10a. A watercoolant groove 27 may also be formed in the tip body portion 10.

FIG. 4 shows the subsequent stage in the manufacture of the first tipbody portion 10. A quantity of a liquid 52, which may be molten wax, isthen poured into the manifold cavity 10a. In order to prevent escape ofthe molten wax, the passage ways 10c and 14 are plugged up. For example,the tip body portion 10 may be placed in a recess in a block 50 intowhich it fits snugly. The quantity of wax is selected such that itsupper surface 52a corresponds to the desired shape of the membraneseparating manifolds 16 and 22 which is to be formed. The wax 52typically fills those passageways 14 in the face plate 12 which have nothad tubes 18 inserted therein, and will also extend into the furtherpassageways 10c, as indicated. The wax 52 is then allowed to harden.

After the wax 52 has hardened, a second liquid material 54, typically ahardening epoxy resin/hardener mixture, is poured into the manifoldcavity 10a, over the wax 52. The second liquid material 54 is permittedto harden, sealing the tubes 18 to the inner wall surfaces of themanifold 16. When the second liquid material 54 has hardened, it formsthe membrane 20 between the first and second manifolds 16 and 22 (FIG.1).

A second liquid material 54 should be selected which does not shrinksubstantially upon hardening, so that it seals the tubes 18 to oneanother effectively and forms a leakproof membrane upon hardening, andwhich does not liquefy under the same conditions as the first liquidmaterial 52, so that the first material 52 can be reliquefied withoutdisturbance of the hardened second material 54.

FIG. 5 shows the last stage in manufacture of the first tip body portion10. In this stage, the first liquid material is reliquefied and removed.For example, if wax is used as the first liquid material, tip bodyportion 10 is simply warmed, such that the wax 52 melts and runs out ofthe unplugged passageways 14 and 10c. The assembly shown in FIG. 5remains. As shown, the membrane 20 seals the tubes 18 to the innersurface of first manifold cavity 10a and also separates the firstmanifold 16 from the second manifold 22 (FIG. 1).

The second and third body portions 24 and 36 can now be assembled to thefirst body portion 10, and the fluted tube 28 inserted through thecentral passageway 26, completing the assembly of the torch tipaccording to the invention.

While a preferred embodiment of the invention has been shown anddescribed, it will be appreciated that there are additionalmodifications and improvements that can be made thereto withoutdeparture from its essential spirit and scope. In particular, a firstpowder material could be substituted for the liquid wax, and a secondhighly viscous material for the epoxy; so long as they did not mix, andthe first material could be removed without disturbance of the second,the method of the invention would be practical. Similarly, the firstmaterial could be removed by a solvent or other means not necessarilyrequiring heating. Accordingly, the recitations made in the followingclaims are to be accorded a substantial range of equivalents, and theinvention is not to be limited by the above exemplary disclosure.

I claim:
 1. Method for manufacture of a torch for mixing of oxidant andfuel gases externally to said torch, comprising the steps of:forming afirst torch body portion, said first body portion having a firstmanifold cavity formed therein having one open side, and said first bodyportion comprising a torch face plate, said torch face plate having aplurality of passageways formed therethrough, extending from said firstmanifold cavity to an external surface of said torch face plate;assembling to said torch face plate a number of gas tubes less than thenumber of said plurality of passageways, each said gas tube terminatingat one end in one of said passageways in said torch face plate andextending from said face plate through and beyond said first manifoldcavity; pouring an amount of a first material into said first cavity,the amount of such material being such that the upper surface of saidmaterial coincides with a desired surface of said first manifoldcorresponding to said open side of said first manifold cavity in saidfirst tip body portion; pouring an amount of a second material, whichdoes not mix with said first material and which is not susceptible toremoval under certain conditions which would remove the first material,over said first material, and around said gas tubes; causing said secondmaterial to harden, such that said hardened second material forms a wallof said first manifold cavity and seals said at least one gas tube tosaid first tip body portion, and said gas tubes extend through the wallof said first manifold thus formed; removing said first material withoutdisturbance of said hardened second material; and providing means forsupply of first and second gases to said gas tubes and to said firstmanifold.
 2. The method of claim 1, wherein said gas passageways nothaving said gas tubes inserted thereinto are formed prior to said stepof pouring a first liquid material into said first cavity.
 3. The methodof claim 1, wherein said means for supply of gas to said at least onegas tube comprises a second manifold into which the ends of said gastubes not terminating at said torch face plate extend.
 4. The method ofclaim 3 wherein said second manifold is formed by a second manifoldcavity in said first tip body portion and a cover member.
 5. The methodof claim 4 wherein said second manifold cavity is separated from saidfirst manifold cavity by a membrane consisting of said wall of saidfirst manifold formed of said hardened second material.
 6. The method ofclaim 1, comprising the further step of assembling an additional tubeassembly to said first body portion, said additional tube assemblycomprising one or more additional passageways for the separate supply ofone or more additional materials to the vicinity of said face plate. 7.The method of claim 6, wherein said additional tube assembly comprisesan externally fluted tube fitting within a cylindrical passageway formedin at least said first tip body portion, such that a first passagewayfor a first material extends down the center of the tube and one or morefurther passageways for further materials are formed between the flutesand the cylindrical passageway in at least the first tip body portion.8. The method of claim 7, wherein plural flutes are formed in saidexternally fluted tube, and said cylindrical passageway in at least saidfirst tip body portion communicates with a further manifold by which thepassageways formed by said plural flutes are in communication with oneanother.
 9. The method of claim 1, wherein said first material is moltenwax.
 10. The method of claim 1, wherein said second liquid material isan epoxy resin/hardener mixture.